First, I realize that this question was asked back in Jan 2017, but it was difficult to obtain useful data because the details of construction were not available.
This question arises as a spin-off of a recent question about the cost-effectiveness of the wall. It seems to me that before one can discuss the cost-effectiveness, it is necessary to have a handle on the "cost".
I am NOT interested in speculation about motivations of people, or how specific individuals would behave.
Almost two years later, is there any better estimate for the cost of a completed border wall project?